Light sensitivity ratings conforming to the international standard set by the International Standards Organization (ISO) are known as ISO ratings and denote a sensitivity of an imaging sensor of an acquisition device to an amount of light present. In digital acquisition devices, altering the ISO rating is a means of exposure control, which affects shutter speed and/or lens aperture. The higher the ISO rating, the more sensitive the imaging sensor, thereby leading to increased exposure of an acquired image. However, as the light sensitivity increases, the imaging sensor is capable of recording a fainter light signal, and thus it will be susceptible to recording noise.
Noise produced by an imaging sensor is undesirable and can appear in an image as numerous small red-pixel cluster artifacts, also known as noise speckles. The presence of noise speckles in an image degrades the operation of conventional red eye detection methods, such as disclosed in U.S. patent application Ser. No. 11/282,955 (FN128). Conventional red eye detection methods involve segmenting and labeling pixels or groups of pixels of an image into candidate red-eye regions. When such red eye detection methods are applied to images having a high ISO rating, many of the noise speckles are initially mistaken for red eye defects, and as a result, the segmenting and labeling operations of the method become computationally burdensome.
It is known to apply a face tracker/detector, such as disclosed in International Patent Application No. PCT/EP2007/005330 (FN143/171/175/161/185PCT) and International Patent Application No. PCT/EP2007/006540 (FN182/214/232PCT), to limit the application of the red eye detection method to confirmed face regions. However, the presence of noise speckles can also affect the accuracy of face detection/tracking. Thus, such an approach could introduce a further degree of error resulting in less accurate red-eye detection.
Furthermore, the computational requirements involved in running typical face detection/tracking prior to running red-eye detection would degrade or limit the performance of the face detector/tracker, the red-eye detector or both, particularly when implemented on real time image acquisition devices.